可变几何截面增压器/废气再循环对重型柴油机性能和排放的影响

Effect of VGT/EGR system on performances and emissions of heavy-duty diesel engine

将HOLSET400可变几何截面增压器(VGT)应用于CA6DL2-35E3重型柴油机上,并在涡前位置建立了高压回路废气再循环(EGR)系统。在ESC测试循环下分别进行了VGT及VGT/EGR的性能规律试验。试验发现配备此VGT系统的柴油机,试验目标参数均存在特定的VGT开度拐点,而对性能改善最明显的开度均出现在拐点附近。因此采取拐点控制VGT开度可充分发挥VGT的效能,改善除NOx外其余气体排放及燃油经济性。通过VGT驱动废气回流可实现28%高EGR率(转速1330 r/min、25%负荷率)。试验目标参数存在特定EGR率拐点(NOx除外),而在拐点对应EGR率范围内降低NOx排放的同时不会对发动机其他性能参数产生太大影响,具备综合优化发动机气体排放和燃油经济性的潜力。

A HOLSET 400 VGT turbocharger was applied on the CA6DL2-35E3 type heavy-duty common-rail diesel engine and a high-pressure-loop EGR system was set up. The performance tests of the engine with the VGT alone and the EGR/VGT respectively were carried out under the ESC test cycle. It is found that in the engine with VGT, there are always specific inflexions in the test objective parameter versus turbocharger control pressure（VGT vane position or opening） curves, and the VGT vane positions corresponding to the best engine performance all are in the nearby of the inflexion. So, it is possible to bring the potential of VGT into full play by the inflexion control to cut the emissions except NOx and improve the fuel economy. Using the strategy of EGR driven by VGT, an EGR rate as high as 28% can be achieved at 1330 r/min and 25% load. There are also inflexions in the test objective parameters（except NOx）versus EGR rate curves, and within the EGR rate corresponding to the inflexion, it is possible to cut the NOx emission by EGR without or with only a little penalty onother engine parameters, demonstrating a comprehensive potential to optimize the emission and economy performances of the diesel engine.